The present invention is directed to a process for detecting ground faults that occur in an electric power transmission line that has a plurality of phase conductors. In particular, upon the response of a protective device, the currents and voltages from these conductors are monitored with respect to a plurality of threshold values. A fault identification signal is generated when at least one conductor current exceeds one of the threshold values or when at least one conductor voltage drops below another one of the threshold values. The fault indication signal is indicative of a single-pole or multi-pole fault.
Previously proposed systems of this type have been discussed, for example, by H. Titze, "Faults and Fault Protection in Three-Phase Power Systems", 1953 Vol. 2, p. 48, and by H. Clemens and K. Rothe, "Protection Methods in Electric Power Systems", 1991, p. 211. Disadvantages that are found in such previously proposed systems include an inability to reliably distinguish single-pole from multipole ground faults and an inability to pinpoint which phase conductor has experienced the detected fault.